1. Field of the Invention
The present invention relates to a process for preparing antirust components and, particularly, to an improved process for preparing polymer antirust components having high and controlled viscosity as well as high basicity, said components being mainly characterized by their improved flowability and capillary penetration, and by a better corrosion strength.
2. Prior Art
Fat and antirust compositions with improved porperties for several uses, and particularly for preventing rust in underbody and motor vehicle boxed parts, have been already described in Mc Millen, U.S. Pat. Nos. 3,242,079 and 3,372,115; in Adams, U.S. Pat. No. 3,565,672, in Rogers, U.S. Pat. Nos. 3,661,622 and 3,746,643; in Hunt, U.S. Pat. No. 3,816,310 and in Italian Pat. No. 858,289.
So U.S. Pat. Nos. 3,242,079 and 3,372,115 relate particularly to compositions for the use as anticorrosive agents for metal surfaces. Said compositions are obtained as fat-like compounds by reacting an alkaline-earth metal sulfonate containing a homogeneous colloidal dispersion of same metal carbonate, both being dissolved in a base flowing lubricating oil, with a hydrogen active containing compound (for example acetic acid or water-alcohol mixture). This reaction is carried out in two steps: in the first step the colloidal dispersion of the alkaline-earth carbonate in oil solution of the sulfonate is obtained; whereas in the second step, after filtering, conversion of said colloidal dispersion of the alkaline-earth carbonate in oil solution of the sulfonate is obtained; whereas in the second step, after filtering, conversion of said colloidal dispersion into fat product was carried out by reacting with the water-alcohol mixture and the hydrogen active compound. According to Mc Millen, the water-alcohol mixture level (generally methanol, or an alcohol with a low carbon atoms content), referred also to as "converting mixture", requested for having the colloidal dispersion conversion, is from about 1 to about 80% by weight, based on colloidal dispersion weight.
U.S. Pat. No. 3,565,672 claims the use of a composition of the above mentioned type as "primer" or undercoater for coating a metal surface before final painting.
U.S. Pat. No. 3,661,622 relates to an improvement in the use of the fat product as "primer", said improvement being attained incorporating in a major amount of said product a lower amount (0.1 to 25% by weight) of a polymer having low crystallinity rate, a molecular weight ranging from 3000 to about 1000000, high solubility in paraffin hydrocarbon solvents and belonging to terpenes, or amorphous polypropylenes, or low molecular weight polyethylenes, or ethylene-vinyl acetate class. According to the inventors, improvement lies in forming a less sticky, more adherent and more anticorrosive primer protective layer, which is applied to surfaces without any particular treatment of the same, and it may be easy coated with any usual surface paint.
U.S. Pat. No. 3,746,643 claims the same fat-like composition, obtained by means of one or two steps processes, to which a microcrystalline wax in an amount ranging from 0.5 to 60 parts by weight is added. The composition thus obtained can be used as component of antirust fats or formulations, and it exhibits improved properties in comparison to the formulations described in U.S. Pat. No. 3,242,079, in that films obtained therefrom are less sticky, last longer, and inhibit better rust formation.
Object of U.S. Pat. No. 3,816,310 is a one step process for preparing fat-type compositions to employ as components of antirust fats or products formulations, in which the filtration step, described in Mc Millen patents, is omitted. The colloidal dispersion of alkaline-earth carbonate in oil solution of alkaline-earth sulfonate is here heated in a controlled fashion, so as to achieve the modification reaction leading to the end product of greasy consistence. Modification is achieved with the presence of water-methanol mixtures, and the heating control is indicated by the expression: EQU t=0.75+1.6.times.(2.5-m)
wherein t means the time (in hours) within which the reaction mixture has to be held between 50.degree. and 100.degree. C., and m is the molar ratio between water and calcium present as carbonate. According to said patent, total water and alcohol level used for the conversion is higher than 80% by weight, based on total weight of alkaline-earth sulfonate and carbonate.
The products described in all the patents mentioned above are actually components for preparing finished formulations employed in industry for the several purposes stated above.
One of these purposes, it being also the purpose for which the products of the present invention are actually intended, is of being applied to parts of motor vehicle body requiring severe antirust treatments.
The fat-like products described in the above mentioned patents are characterized by thixotropy, poor flowability, good resistance to corrosion due to moisture and calcium chloride, good heat stability.
However, said compositions, even though more or less substantial amounts of waxes or amorphous polymers are added thereto, exhibit notable technological and applicability restrictions when end-formulations containing them are employed to protect from rust body underlying parts, and particularly motor vehicle boxed parts. As said parts are for their own nature only hardly penetrated by antirust formulations having a given viscosity, whichever the application system utilized for said penetration may be, it results that when application is over, a given, more or less important portion of the total surface to be protected is not coated with protective layer. In these uncoated parts, rusting starts slowly its growing, and it spreads out even under the protective film where it was able to set, thus forming further rust. The above mentioned deficiencies have to be ascribed to a reduced formulation ability, and particularly to the thyxotropic and fat-like component, to freely and easy penetrate all the holes present in the boxed parts. Reduction of thixotropic compound level in end-formulations, or dilution of said formulations with several solvents to make them flowing, and therefore more penetrating and coating, provides in practice a light enhancement of the coated surface, without having yet a full coating, but also and chiefly it provides a contemporary reduction in thickness of the film which has been deposited and, consequently, a reduction of the protective strength against rust forming.
For this reason, consumers of the end-formulations which should be applied to underbody and motor vehicle boxed parts, request to purchase specification certain flowability and capillary penetration properties, which by nature correspond to maximum possibilities offered by products presently on the market. Consumers are really constantly in search of formulations having still better requirements.
A further disadvantage of the products presently on the market, is due to unhomogeneity sometimes noticeable in different lots or supplies of the thixotropic component, which is bound to viscosity values at times considerably different (for example from 200,000 to about 500,000 cps at 23.degree. C.).
In order to respect the viscosity values of the formulations, which have been forced by consumers within sometimes rather narrow limits, producers of said formulations are therefore obliged to continuous settlements of the same.